According to these theories, the potential for rationality is inherent in communication itself. Along this argument, Habermas has formulated a notion of communicative rationality which takes up this implicit potential and formalizes it into explicit knowledge. The goal is to transform implicit know-how into explicit know-that. In this case, the phenomena that needs to be explicated are the intuitively mastered rules for reaching an understanding and conducting argumentation possessed by subjects capable of speech and action. The result is a complex conception of reason that Habermas sees as doing justice to the most important trends in twentieth century philosophy, while escaping the relativism which characterizes postmodernism, and providing standards for critical evaluation (Habermas, 1992).

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There are number of specific trends that Habermas identifies as important to twentieth century philosophy, and to which he thinks his conception of communicative rationality contributes. To look at these trends is to give a clear outline of Habermas's understanding of communicative rationality. He labels all these trends as being post-metaphysical. (Cooke, 1994) These post-metaphysical philosophical movements have, among other things:

cast doubt on the idea that reason should be conceived abstractly beyond history and the complexities of social life, and have contextualized or situated reason in actual historical practices;

replaced a focus on individual structures of consciousness with a concern for pragmatic structures of language and action as part of the contextualization of reason; and

given up philosophy's traditional fixation on theoretical truth and the representational functions of language, to the extent that they also recognize the moral and expressive functions of language as part of the contextualization of reason.

Habermas's conception of communicative rationality moves along with these contemporary currents of philosophy. Concerning 1) it can be said that:

[Communicative] rationality refers primarily to the use of knowledge in language and action, rather than to a property of knowledge. One might say that it refers primarily to a mode of dealing with validity claims, and that it is in general not a property of these claims themselves. Furthermore…this perspective suggests no more than formal specifications of possible forms of life… it does not extend to the concrete form of life…(Cooke, 1994).

Concerning 2), Habermas clearly and explicitly understands communicative rationality according to the terms of a reconstructive science. This means that the conception of communicative rationality is not a definitive and final rendering of what reason is, but rather a fallible but rigorously substantiated claim or hypothesis. It also means that communicative rationality itself is a procedural and falliblistic ideal of rationality. It can prescribe only formal specifications concerning what qualifies as reasonable (not concrete exemplars to be emulated) and even those formal specifications are taken as fallible, being open to revision in light of experience and learning.

On 3) and 4), Habermas's entire conceptual framework is focused around social interaction and communication, and he ties rationality to the validity basis of everyday speech. It contextualizes reason in the everyday practices of modern individuals. This is against philosophies (e.g. Plato, Kant, etc.) that sought to ground reason in an intelligible and non-temporal realm, or view from nowhere, which supposed that reason was able to judge the realm of time and contingency from an outside perspective.

While Habermas's notion of communicative rationality is contextualized and historicized, it is not relativistic. Many philosophical contextualists take reason to be entirely context-dependent and relative. Habermas holds reason to be relatively context specific and sensitive. The difference is that Habermas explicates the deep structures of reason by examining the presuppositions and validity dimensions of everyday communication, while the relativists focus only on the content displayed in various concrete standards of rationality. Thus, Habermas can compare and contrast the rationality of various forms of society with an eye to the deeper and more universal processes at work, which enables him to justify the critique of certain forms (i.e., that Nazism is irrational and bad) and lend support to the championing of others (i.e., democracy is rational and good). The relativists on the other hand can compare and contrast the rationality of various forms of society but are unable to take up a critical stance, because they can posit no standard of rationality outside the relative and variable content of the societies in question, which leads to absurd conclusions (i.e., that Nazism is morally equivalent to democracy because the standards for both are relative).

Concerning 5), Habermas's communicative rationality emphasizes the equal importance of the three validity dimensions, which means it sees the potential for rationality in normative rightness (WE), theoretical truth (IT) and expressive or subjective truthfulness (I). The differentiation of these three “worlds” is understood as a valuable heuristic. This leaves each to its specific forms of argumentation and justification. However, these validity dimensions should be related to one another and understood as complementary pieces in a broader conception of rationality. This points towards a productive interpenetration of the validity dimensions, for example the use of moral insights by the sciences without their having to sacrifice theoretical rigor, or the inclusion of psychological data into resources of moral philosophy.

These last points concerning the breadth of communicative rationality have by far the most important implications. By differentiating the three validity dimensions and holding them as equally valuable and rational, a broader and multifaceted conception of rationality is opened. What this means is that Habermas has, through the formal pragmatic analysis of communication, revealed that rationality should not be limited to the consideration and resolution of objective concerns. He claims that the structure of communication itself demonstrates that normative and evaluative concerns can (and ought to) be resolved through rational procedures.

The clearest way to see this is to recognize that the validity dimensions implicit in communication signify that a speaker is open to the charge of being irrational if they place normative validity claims outside of rational discourse. Following Habermas, the argument relies that the following are given:

(a) that communication can proceed between two individuals only on the basis of a consensus (usually implicit) regarding the validity claims raised by the speech acts they exchange;

(b) that these validity claims concern at least three dimension of validity (I, truthfulness; WE, rightness; IT, truth); and

(c) that a mutual understanding is maintained on the basis of the shared presupposition that any validity claim agreed upon could be justified, if necessary, by making recourse to good reasons.

From these premises it is concluded that any individual engaging in communication is accountable for the normative validity of the claims they raise. By earnestly offering a speech act to another in communication, a speaker claims not only that what they say is true (IT) but also that it is normatively right (WE) and honest (I). Moreover, the speaker implicitly offers to justify these claims if challenged and justify them with reasons. Thus, if a speaker, when challenged, can offer no acceptable reasons for the normative framework they implied through the offering of a given speech act, that speech act would be unacceptable because it is irrational.

In its essence the idea of communicative rationality draws upon the implicit validity claims that are inescapably bound to the everyday practices of individuals capable of speech and action. A mutual understanding can be achieved through communication only by fusing the perspectives of individuals, which requires they reach an agreement (even if it is only assumed) on the validity of the speech acts being shared. Moreover, the speech acts shared between individuals in communication are laden with three different types of validity claims, all of which quietly but insistently demand to be justified with good reasons. Communicative rationality appears in the intuitive competencies of communicative actors who would not feel that a mutual understanding had been achieved if the validity claims raised were unjustifiable. Thus, the simple process of reaching an understanding with others impels individuals to be accountable for what they say and to be able to justify the validity claims they raise concerning normative (WE), evaluative (I) and objective matters (IT).

Of course a very important issue arises from this, which is that what constitutes a good or acceptable justification varies from context to context. Even if it is accepted that rationality must be expanded to include normative and evaluative dimensions, it is not clear what it is that makes a speech act justified, because it is unclear what constitutes a good reason.

It must be understood that there are different kinds of reasons in relation to the different validity dimensions. This is apparent, because what defines a validity dimension are the procedures of justification that are unique to it. For example, if one claims or implies with their speech act that it is raining outside, a good reason for claiming this is that one saw it out the window. If this were called into question, the claim would be vindicated by looking out the window. This is a very simple way of describing the procedures of justification unique to objective validity claims. However, if one claims or implies with their speech acts that 'abortion is acceptable in certain cases', one's reasons for claiming this must be of a different nature. The speaker would have to direct the attention of the listener to certain features of the social world that are infused with meaning and significance. The speaker would have to draw on insights into, for instance, the vulnerability of individuals under the weight of life's circumstances, the kinds of rights that humans deserve, etc. These types of considerations make up the resources available for the justification of normative validity claims.

What constitutes a good reason is a more complex problem. Accepting the distinction between the different kinds of reasons that accompany the differentiation of the validity dimensions does not give any insight into what a good reason in a particular validity dimension would be. In fact, it complicates the issue because it makes it clear that there are different procedures unique to each validity dimension and that these dimensions cannot be reduced to one another. Habermas does suggest some general guidelines concerning the rationality of communicative processes that lead to conclusions (see Universal pragmatics). But his explanations regarding the specific procedures that are unique to each validity dimension are much more elaborate.